Abstract
This paper attempts to study the effect of different strengthening methods on recycled coarse aggregate (RCA) reprocessed from construction and demolition (C&D) waste. And it aims to obtain the optimal RCA content in cement stabilized recycled mixture (CSRM) applied in the base layer of pavement. Firstly, three strengthening methods were used to strengthen the RCA. It was revealed that the sodium silicate solution is the best method in a strengthening concentration of 8% and strengthening for five hours. Then, the mechanical experiments under two cement dosages, including unconfined compressive strength, splitting strength, and compressive rebound modulus tests, were carried out. In each cement dosage, five different RCA contents (0%, 25%, 50%, 75%, and 100%) were considered. It was found that, at 5% of cement dosage, the strength of CSRM satisfied the requirements of the base layer of the expressway under heavy traffic load. In the case of 4% of cement dosage, the strength of CSRM which was beyond 50% of RCA content was failed to meet specification requirements. For the failed cases, by strengthening RCA in the best method obtained before, 7 d unconfined strength and crushing value of the CSRM with 50% RCA content could meet the requirements of the subbase of expressways and first‐class highways in China; the 75% of the mixture meets the requirements of the second‐class highways and below.
Highlights
Introduction e rapid development ofChina’s urbanization has resulted in massive generation of construction and demolition (C&D) waste, and it represents more than 30% of the world’s municipal solid waste, 2 billion tons in 2019 [1]
Utilization of recycled coarse aggregate (RCA) into the pavement construction industry contributes to improving the efficiency and sustainability by conservation of raw materials and reduction of the landfilled C&D waste amount and greenhouse gas emission [7,8,9,10]
Taking the dosage of 4% cement as an example, when the content of RCA increased from 0% to 100%, the unconfined compressive strength from 7 d to 28 d increases by an average of 35.02% compared to the stage from 28 d to 90 d
Summary
According to the method of Chinese standard “Highway Engineering Aggregate Test Regulations” [39], the basic properties of the RCA with 3 different particle sizes were studied. Us, the water absorption rate and crushing value of recycled brick aggregates are larger than those of recycled concrete aggregates [41, 42]. Recycled fine aggregate (1) As the content of RCA increases, the MDD of the CSRM decreases and its OMC increases, regardless of the cement dosage. En, the compaction experiments were conducted to research the OMC and the MDD under different contents of RCA and cement dosage.
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